1. Field of the Invention
The present invention generally relates to maintenance of wired/cable communication systems and, more particularly, to detecting and reporting locations of flaws in shielding integrity in the communication system based on signal egress and reporting and remediation thereof.
2. Description of the Prior Art
Wired communication systems have been known for many years and, due to the initial simplicity and limited usage and bandwidth of early systems, the wiring structure was not generally critical to the performance thereof and did not tend to affect operation of other devices proximate thereto or wireless communication systems. At the present time, however, wired communication systems (often referred to as cable telecommunications systems or, simply as cable communications systems or cable systems) use high frequency carrier signals to provide increased bandwidth and information transmission capacity as well as to accommodate digital signaling at very high bit rates. Such high frequency carriers require the use of shielded coaxial cables for efficient transmission while demands for wireless communication bandwidth has resulted in overlap of wireless communication frequency band allocation with the frequency band currently used for wired communications, as is made possible, at least theoretically, by the fact that the required shielding maintains separation between wired and wireless communications operating in the same frequency bands. At the present time, the frequencies allocated for wired cable distribution and communication systems substantially overlaps or is overlapped by the frequency band used for commercial aircraft communication and navigation. Therefore, the possibility of signal leakage from a wired communication system is quite critical and wired systems must be constructed and maintained to limit radiation therefrom, referred to as signal egress, below stringent limits under Federal Communications Commission regulations.
However, a shielding flaw in a wired communication system has substantially symmetrical or complementary effects and thus also permits signal ingress from the environment where electromagnetic signal components at the frequency band(s) of interest are becoming greater over time. From the standpoint of a cable communication system operator, signal ingress is a severe problem, particularly for digital communications, since corruption of a digital signal packet beyond the degree which can be recovered using error correcting codes (ECCs) and the like requires retransmission of the packet. The time required for detection of the error and retransmission of packets containing unrecoverable errors slows system operation and reduces capacity of the system.
Accordingly, detection and correction of flaws in shielding integrity is critical to both wired and wireless communications. At the same time, increases in communications, generally, have resulted in continuing increases in electromagnetic signals in the frequency band of interest which complicates signal egress detection.
While receivers of very high sensitivity and selectivity have been developed for signal egress detection, sufficient monitoring of a cable communication system to provide adequate maintenance generally requires substantially constant monitoring of the entire geographic extent of the cable communication system using such receivers in vehicles traveling on public roads which may or may not be proximate to the route of communications cables to detect signals which may represent signal egress. To facilitate this process, a signal egress detection system developed by Comsonics, Inc. of Harrisonburg, Va., the assignee of the present invention, has developed a system that combines a suitably sensitive receiver with a global positioning system to automatically capture the location at which signals that possibly represent signal egress from the cable system are detected and prepares a report that can be immediately transmitted to a central facility or stored and later downloaded. Such reports can then be automatically converted to work repair orders to be executed by crews employed by the cable operator to find the shielding integrity flaw and effect repairs.
However, such procedures can result in many reports and work orders which are effectively duplicates and may contain errors due to interference signals being detected as potential signal egress. Some systems have been developed to validate a detection at a particular frequency as signal egress rather than simply interference signals, but merely sorting even validated reports by location where a validated egress signal is detected, while sufficient for system maintenance, is insufficient to avoid a large number of duplicate work orders since the signal radiation pattern from a shielding integrity flaw without prior information in regard to the nature (e.g. geometry) of the flaw is not readily predictable and a single flaw may be detectable from numerous locations; leading to unnecessary costs and reduced efficiency of operation of the cable communication system.